Handle missing Living Greengrass page

[lyonsquark]

The Living Greengrass page has the date in the URL (this is unfortunate). Sometimes, the blog post comes out a day late, so it will have a date that does not exactly correspond to the daf date. Maybe figure out a way to try the URL and it get a 404, then advance the date. Of course this won't work if the blog isn't posted yet, but it may work for dafs in the past. Kinda tricky.